Objectives: Health inequity across social classes is closely associated with unequal healthcare utilization, and there have been sustained efforts to improve healthcare accessibility. Public healthcare insurance is one attempt to eliminate such health inequities. The purpose of this study was to examine a horizontal equity index for dental service utilization, which included diverse factors affecting health inequity, such as personal health and social context variables. Methods: The 2008 to 2011 outpatient datasets of the Korean Healthcare Panel were analyzed. Zeroinflated negative binomial regression (ZINB) was conducted to estimate need-adjusted healthcare use with the following independent variables: health outcome (EQ-5D), chronic disease, and the Composite Deprivation Index. The concentration index and horizontal inequality index were calculated for the actual use of dental services and resource use-based dental visits. Results: The ZINB regression analysis showed that age and personal health level on the EQ-5D were significant predictors, and the Composite Deprivation Index was influential. The concentration index for dental service utilization indicated that there was inequity favoring high-income brackets, but there was inequity favoring low-income groups when health level was taken into account. Overall, the horizontal equity index for dental service utilization estimated based on the two values was positive, meaning that there was inequity favoring high-income groups. Conclusions: The use of dental services has been steadily on the rise, and dental service accessibility and public healthcare coverage seem to have expanded. However, when the horizontal equity index for dental service utilization was estimated based on health level, there was inequity, with high-income groups making more use of dental services. Thus, equal access to dental services is not guaranteed, despite the adjustment for need. Methods of increasing dental service use in different income brackets must be carefully considered to remove disparities in the use of dental services.